#surfacetension — Public Fediverse posts

Urinal Dynamics Win Ig Nobel Prize

Thirteen years ago, I made a prediction that work on how to avoid urinal splashback would win an Ig Nobel Prize. Today, I am, at last, vindicated. Randy Hurd, Zhao Pan, Tadd Truscott, and Kaveeshan Thurairajah shared the 2026 Ig Nobel Prize in Physics for their work designing a splash-free urinal.

The culmination of this decade-plus of research are two urinal designs, the Cornucopia (“Cornucopeea”) and the Nautilus (“Nauti-Loo”). Both designs minimize splash, in part, through their geometry. As you may have noticed when rinsing dishes, having a stream of droplets hit a surface at a high impact angle creates lots of splash. But at a low impact angle, very little splash occurs. The team took this observation and created designs that minimized impact angle no matter where a user aimed.

Naturally, they tested the two new designs, alongside two existing urinal designs, finding that the new urinals reduced splashing by as much as 95% across a range of flow rates and user heights. Although the Cornucopia was the least splashy urinal, the team gave the Nautilus an overall edge because its design is easier to clean and works for children, adults, and wheelchair users.

Considering the estimated 1 million liters of urine contemporary urinals splash across U.S. restrooms daily, the Nautilus could save significant labor and cleaning costs, if implemented. (Image credits: urinals and experiment – K. Thurairajah et al., poster – R. Hurd et al.; research credit: K. Thurairajah et al. and R. Hurd et al.)

P.S. – As indicated, I’ve followed this work for a long time. In addition to this post, we did a webcast (10 years ago, yikes!) that touched on the topic. But my most in-depth coverage of the story is still to appear in print; you’ll get to enjoy the whole tale–stretching all the way back to 2012–in a chapter of my forthcoming book. More on that soon! In the meantime, please enjoy this gem of a scientific poster from the project’s early days in 2013:

Flex Pen and Ink

It’s no secret that I’m a fan of fountain pens. They’re just one way I like to have little celebrations of fluid physics in my everyday life. That said, I don’t typically use anything with a monster flex nib like what you see here. This is extra. But it’s also an incredibly cool glimpse of fluid physics.

Just check out that sheet of fluid stretching between the tines! To keep the liquid sheet intact to that kind of width you need the perfect balance of surface tension and flow. The ink needs to cling to the tines, cohere to itself (despite some impressive stretching), and make its way down from the reservoir and through the feed quickly enough (but not too quickly!) to replace the ink being laid down on the page as the nib moves. Gorgeous stuff. (Video and image credit: Flexperiments)

Giant Water Balloon to the Face

It’s the summertime, so Gav and Dan of the Slow Mo Guys are back to experimenting with giant water balloons. In this video, they send several careening down a slope into Dan’s face. Watching the balloons descend and pop is (unsurprisingly) my favorite part. It’s neat to see how the elasticity of the balloon acts like a beefed-up surface tension to make this enormous blob of water act like an oversized droplet. (Video and image credit: The Slow Mo Guys)

A Fluidic Space Telescope

A telescope’s resolution is set by the size of its reflective surface. Our largest space telescope, JWST, has a 6.5-meter reflector, the largest we could manage given manufacturing constraints and the need to launch it in a rocket. To reach even larger sizes, researchers are considering a new type of reflector: one made of liquid.

A fluidic telescope has some obvious advantages: surface tension makes it atomically smooth, and liquids can be packed into any convenient shape for launch. But there are challenges, also. Like, what happens to the reflector when you point it in an new direction?

That’s what this study looks at, mathematically. Using a mathematical model of a 50-meter-wide, millimeter-thick fluid, the researchers analyzed how different maneuvers over the telescope’s lifetime would affect the image quality.

Shifting the reflector creates perturbations in the surface, initially at the mirror’s edges. Over time, those perturbations move toward the center of the mirror and, at the same time, decay. The team found that, while typical space telescope operations distorted parts of the mirror beyond the limits of good optical quality, the inner 80% of the mirror could remain undisturbed for twenty or more years. That would be like having a 40-meter telescope in orbit with more than 6x the resolution of JWST. (Image credit: NASA; research credit: I. Gabay et al.)

Droplets Can Climb Sugar Fibers

In nature, droplets and fibers can meet on a spider’s web, on fur, or on a dew-gathering cactus. Here, researchers explore what happens when the droplet can dissolve the fiber it’s suspended on. As the authors note, a lumberjack who cuts the branch they sit on makes a fatal choice. The droplet sees a different outcome.

As the droplet hangs on the fiber, it dissolves the fiber’s sugar. Dense, sugar-laden water flows downward along the fiber and a replenishing upward flow goes along the droplet’s exterior. Because the sugar concentration is lower near the top of the drop, the fiber thins most quickly there.

The droplet has capillary forces along its top and bottom, where it meets the fiber. At the top, the droplet is free to expand, wetting more fiber, but the bottom of the drop is pinned to the fiber. The excess capillary force there goes into compressing the fiber.

As soon as the fiber breaks, the capillary force is no longer balanced, and the droplet jumps upward. If the drop and fiber are sized just right, the drop will jump upward enough to stay attached to the fiber instead of falling off. (Image and research credit: S. Dorbolo et al.)

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“Stellar Iris”

Artist Thomas Blanchard likes to create wild visuals from a mixture of mundane ingredients like ink, soap, oils, and ferrofluids. In this latest video, he’s mixed chemical reactions and physical phenomena into something reminiscent of a god’s eye staring across time and space, creation and destruction. (Video and image credit: T. Blanchard)

Why does water have such an unusually high surface tension?

This study links the effect to molecular-scale interactions and hydrogen-bond dynamics, offering new insight into one of water’s most fundamental properties.

🔗 https://pubs.aip.org/aip/pof/article-abstract/38/4/042007/3386944/Molecular-driven-extreme-surface-tension-of-water?redirectedFrom=fulltext

#SurfaceTension #Water #MolecularPhysics #FluidDynamics #interfaces

Plucking Droplets

A sudden breeze can pluck droplets hanging from a stem. Here, researchers recreate that phenomenon in the laboratory. With a close-up view and high-speed images, we can enjoy every detail of the detachment and break-up. As the wire pulls away, it drags a liquid sheet off the droplet. The thicker rims on either side of the sheet eventually collide, creating a jet that stretches, deforms, and, at last, breaks. (Video and image credit: D. Maity et al.)

Making a Star-Shaped Droplet

We usually think of surface tension turning droplets into spheres in order to minimize their area. But spheres aren’t the only shape surface tension can enforce. Here, researchers suspend tiny droplets of oil in a soapy fluid. At the right temperature, these droplets form a crystalline surface while the fluid within remains liquid. As in the fully liquid droplet, surface tension tries to minimize the shell’s surface energy, enabling it to take on many different shapes.

In this study, researchers demonstrate that the shell-enclosed droplets can even change, reversibly, from a hexagon to a six-pointed star and back. The transformation is shown above, in an experiment that gradually changes the droplet’s temperature–and, thus, its surface tension.

Although shape changes similar to these have been described before, this experiment was the first where the shell’s defects–the vertices of the hexagon–don’t shift during the transformation. (Video, image, and research credit: C. Quilliet et al.; via APS)

A Bubbly Heart

Next time you fill your water bottle, watch closely and see if you can spot a bubble heart like these. When a jet falls into a pool, it pulls air in with it. The low pressure of the jet pulls bubbles inward, even as shear pulls the bubbles downward with the sinking liquid. If the bubbles are large and there’s enough momentum in the jet, the lower portion of the bubble will get pulled into a conical shape, while the upper portion remains a hemisphere. That forms one lobe of the heart. The other half requires a second bubble. But with a little patience and luck, you can form a complete heart. Happy Valentine’s Day! (Image credit: S. Tuley et al.)

Caught in a Spider’s Web

Grains of pollen are caught amid droplets on a spider’s web in this award-winning image by John-Oliver Dum. How droplets behave on fibers has been a popular topic in recent years with research on how droplets nestle into corners, how they slide on straight or twisted wires, the patterns formed by streams of falling drops, and what happens to a droplet on a plucked string. (Image credit: J. Dum; via Ars Technica)

Superwalking Droplets

When placed on a vibrating oil bath, droplets have many wild behaviors, some of which mirror quantum mechanics. Even big droplets — bigger than 2 millimeters in diameter — can get in on the fun. This video shows several of these “jumbo superwalkers” in action, both singly and in groups. (Video and image credit: Y. Li and R. Valani; via GFM)

Marangoni Effect in Biology

For decades, biologists have focused on genetics as the key determiner for biological processes, but genetic signals alone do not explain every process. Instead, researchers are beginning to see an interplay between genetics and mechanics as key to what goes on in living bodies.

For example, scientists have long tried to unravel how an undifferentiated blob of cells develops a clear head-to-tail axis that then defines the growing organism. Researchers have found that, rather than being guided purely by genetic signals, this stage relies on mechanical forces–specifically, the Marangoni effect.

The image above shows a mouse gastruloid, a bundle of stem cells that mimic embryo growth. As they develop, cells flow up the sides of the gastruloid, with a returning downward flow down the center. This is the same flow that happens in a droplet with higher surface tension in one region; the Marangoni effect pulls fluid from the lower surface tension region to the higher one, with a returning flow that completes the recirculation circuit.

The same thing, it turns out, happens in the gastruloid. Genes in the cells trigger a higher concentration of proteins in one region of the bundle, creating a lower surface tension that causes tissue to flow away, helping define the head-to-tail axis. (Image credit: S. Tlili/CNRS; research credit: S. Gsell et al.; via Wired)

A Soft Cell in Microgravity

There are many shapes that can be tiled to fill space, but nearly all of them have sharp corners. Last year, mathematicians identified a new class of shapes, known as “soft cells,” that feature curved edges and faces but very few sharp corners. Like traditional polyhedrals, soft cells can tile to fill a space completely without overlapping or gapping.

Now the researchers, with some help from astronauts aboard the ISS, have brought one of their soft cells to life. Using an edge skeleton to guide the shape, astronaut Tibor Kapu filled the skeleton with water, which, in microgravity, formed a perfect soft cell, complete with faces curved by surface tension to their minimal area. See it in action below. (Image and video credit: HUNOR/NASA; research credit: G. Domokos et al.; via Oxford Mathematics)

https://www.youtube.com/shorts/EyMbqPUKl80

Marangoni Bursting With Surfactants

A few years ago, researchers described how an alcohol-water droplet atop an oil bath could pull itself apart through surface tension forces. Dubbed Marangoni bursting, this phenomena has shown up several times since. Here, researchers explore a twist on the behavior by adding surfactants to see how they affect the bursting phenomenon. (Video and image credit: K. Wu and H. Stone; via GFM)

#flowVisualization #fluidDynamics #instability #MarangoniBursting #physics #science #surfaceTension #surfactant

The Balvenie

Photographer Ernie Button explores the stains left behind when various liquors evaporate. This one comes from a single malt scotch whisky by The Balvenie. The stain itself is made up of particles left behind when the alcohol and water in the whisky evaporate. The pattern itself depends on a careful interplay between surface tension, evaporation, pinning forces, and internal convection as the whisky puddle dries out. (Image credit: E. Button/CUPOTY; via Colossal)

#alcohol #deposition #evaporation #fluidDynamics #fluidsAsArt #physics #science #surfaceTension

Deep Breaths Renew Lung Surfactants + A Special Announcement

Taking a deep breath may actually help you breathe easier, according to a new study. When we inhale, air fills our alveoli–tiny balloon-like compartments within our lungs. To make alveoli easier to open, they’re coated in a surfactant chemical produced by our lungs. Just as soap’s surfactant molecules squeezing between water molecules lowers the interface’s surface tension, our lung surfactants gather at the interface and lower the surface tension, making alveoli easier to inflate.

But things are a little more complicated in our lungs than in our kitchen sink because of our constant cycle of breathing, which stretches and compresses our lungs’ surfaces and surfactant layers. Imagine a flat interface, lined with surfactant molecules; then stretch it. As the interface stretches, gaps open between the surfactant molecules and allowing molecules from the interior of the liquid to push their way to the newly stretched interface, changing the surface tension. If the interface gets compressed, some of the excess molecules will get pushed back into the liquid bulk.

In looking at how lung surfactants respond to these cycles of compression and stretching, the researchers found that the lung liquid develops a microstructure during cycles of shallow breathing that makes the surface tension higher, thus making lungs harder to fill. In contrast, a deep breath like a sigh replenished the saturated lipids at the interface, lowering surface tension and making lungs more compliant. So a deep sigh actually can help you breathe easier. (Image credit: F. Møller; research credit: M.. Novaes-Silva et al.; via Gizmodo)

P.S. — I’ve got a book (chapter)! Several years ago, I joined an amazing group of women to write two books (one for middle grades and one for older audiences) about our journeys as scientists. And they are out now! In fact, today we’re holding a “Book Bomb” where we aim for as many of us as possible to buy the book(s) on the same day. If you’d like to join (and get ahead on your gift shopping), here are (affiliate) links:

• Persevere, Survive, and Thrive (including my story of becoming a science communicator): Amazon, Bookshop.org
• For All the Curious Girls: Amazon, Bookshop.org

#biology #fluidDynamics #lungs #physics #science #surfaceTension #surfactants

Wave Energy Through the Meniscus

Even small changes to a meniscus can change how much wave energy passes through it. A new study systemically tests how meniscus size and shape affects the transmission of incoming waves.

As seen above, the meniscus was formed on a suspended barrier. By changing the barrier size and wettability as well as the characteristics of incoming waves, researchers were able to map out how the meniscus affected waves that made it past the barrier.

In particular, they found that drawing the meniscus upward by raising the barrier would, at first, enhance wave transmission but then suppressed wave energy as the barrier moved higher. They attributed the change in behavior to an interplay between water column height and meniscus inclination. (Research and image credit: Z. Wang et al.; via Physics World)

#capillaryWaves #fluidDynamics #meniscus #physics #science #surfaceTension #waves

“Re:Birth”

In “Re:Birth,” videographer Vadim Sherbakov explores the fascinating patterns of ferrofluids, which suspend tiny ferrous particles in another liquid, often oil. When this magnetic liquid is mixed with ink or paint, its black lines take on a labyrinthine appearance. The result is rather psychedelic, especially with Sherbakov’s bold colors. (Video and image credit: V. Sherbakov)

#ferrofluid #fluidDynamics #fluidsAsArt #instability #physics #science #surfaceTension

Espresso in Slow-Mo

Espresso has some pretty cool physics. But it’s also just lovely to watch in slow motion. This video offers a look at the making of an espresso shot at 120 frames per second (though you can also enjoy a 1000 fps version here). Watching the film form, expand, and break up at the beginning and end of the video is my favorite, but watching how the occasional solid coffee grains make their way into and down the central jet is really interesting also. (Video and image credit: YouTube/skunkay; via Open Culture)

#espresso #flowVisualization #fluidDynamics #fluidsAsArt #highSpeedVideo #physics #science #surfaceTension

@UnterDruck #physics #fedihelp #surfacetension #measurement

Dancing Metal Droplets

Droplets of a gallium alloy are liquid at room temperature. When spiked with aluminum grains and immersed in a solution of NaOH, the droplets change shape and move in a random fashion. This video delves into the phenomenon, describing how a chemical reaction with the aluminum grains changes the local surface tension and creates Marangoni flows that make the droplets move. To get the droplet motion, you need to have the aluminum concentration just right. With too little, there’s not enough Marangoni flow. With too much, the hydrogen gas produced in the chemical reaction disrupts the droplet motion. (Video and image credit: N. Kim)

https://www.youtube.com/watch?v=XYRj0Ty9udo

#2024gofm #chemistry #droplets #fluidDynamics #marangoniEffect #physics #science #surfaceTension

Building a Better Fog Harp

On arid coastlines, fog rolling in can serve as an important water source. Today’s fog collectors often use tight mesh nets. The narrow holes help catch tiny water particles, but they also clog easily. A few years ago, researchers suggested an alternative design — a fog harp inspired by coastal redwoods — that used closely spaced vertical wires to capture water vapor. At small scales, this technique worked well, but once scaled up to a meter-long fog harp, the strings would stick together once wet — much the way wet hairs cling to one another.

The group has iterated on their design with a new hybrid that maintains the fog harp’s close vertical spacing but adds occasional cross-wires to stabilize. Laboratory tests are promising, with the new hybrid fog harp collecting water with 2 – 8 times the efficiency of either a conventional mesh or their original fog harp. The team notes that even higher efficiencies are possible with electrification. (Image credit: A. Parrish; research credit: J. Kaindu et al.; via Ars Technica)

#condensation #elastocapillarity #fluidDynamics #fog #fogCollection #physics #science #surfaceTension

How Insects Fly in the Rain

Getting caught in the rain is annoying for us but has the potential to be deadly for smaller creatures like insects. So how do they survive a deluge? First, they don’t resist a raindrop, and second, they have the kinds of surfaces water likes to roll or bounce off. The key to this second ability is micro- and nanoscale roughness. Surfaces like butterfly wings, water strider feet, and leaf surfaces contain lots of tiny gaps where air gets caught. Water’s cohesion — its attraction to itself — is large enough that water drops won’t squeeze into these tiny spaces. Instead, like the ball it resembles, a water drop slides or bounces away. (Video and image credit: Be Smart)

#biology #butterfly #cohesion #droplets #fluidDynamics #hydrophobic #insects #physics #science #superhydrophobic #surfaceRoughness #surfaceTension

“Legend”

Filmmaker Roman De Giuli returns to his roots with this short fluid-filled film inspired by the color gold. He combines paint, ink, powders, and particles in a mix of micro- and macroscale photography. As always, the results are a mesmerizing plethora of fluid phenomena: Marangoni flows, turbulence, vorticity, viscous fingering and so much more. (Video and image credit: R. De Giuli)

#fluidDynamics #fluidsAsArt #instability #physics #science #surfaceTension #turbulence